Javascript: get a function's value to use in other function

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Javascript

calculator

Hey, hope someone could help. I tried to use other functions value inside a function, but unsuccessful.

What I have tried:

Here what I have done:

<table>
    <tr>
    <td><input type="text" name="r1" id="r1" onkeyup="total_r1()" class="form-control"/></td>
    <td><input type="text" name="s1" id="s1" onkeyup="total_r1()" class="form-control"/></td>
    <td><input type="text" name="t1" id="t1" value="" class="form-control"/></td>
    </tr>
    <tr>
    <td><input type="text" name="r2" id="r2" onkeyup="total_r2()" class="form-control"/></td>
    <td><input type="text" name="s2" id="s2" onkeyup="total_r2()" class="form-control"/></td>
    <td><input type="text" name="t2" id="t2" class="form-control"/></td>
    </tr>
    <tr>
    <td><input type="text" name="r3" id="r3" onkeyup="total_r3()" class="form-control"/></td>
    <td><input type="text" name="s3" id="s3" onkeyup="total_r3()" class="form-control"/></td>
    <td><input type="text" name="t3" id="t3" class="form-control"/></td>
    </tr>
    <tr>
    <td><input type="text" name="r4" id="r4" onkeyup="total_r4()" class="form-control"/></td>
    <td><input type="text" name="s4" id="s4" onkeyup="total_r4()" class="form-control"/></td>
    <td><input type="text" name="t4" id="t4" class="form-control"/></td>
    </tr>
    <tr>
    <td></td>
    <td  style="text-align:center;padding-top:1.5%">TOTAL</td>
    <td style="text-align:center;">
    	<input type="text" name="total_monthclaim" id="total_monthclaim" class="form-control"/>
    </td>

here is my script:

function total_r1(){
    		
    		var r1 = document.getElementById('r1').value;
    		var s1 = document.getElementById('s1').value;
    		
    		var total = (r1*s1);
    		var t_1 = total.toFixed(2);
    		var t1 = document.getElementById('t1');
    		t1_5.value = t_1;
    	}
    	total_r1();
    	
    	function total_r2(){
    		
    		var r2 = document.getElementById('r2').value;
    		var s2 = document.getElementById('s2').value;
    		
    		var total = (r2*s2);
    		var t_2 = total.toFixed(2);
    		var t2 = document.getElementById('t2');
    		t2.value = t_2;
    	}
    	total_r2();
    	
    	
    	function total_r3(){...}
    	total_r3();

        function total_r4(...){}
        total_r4();

    	function total_all(){
    		
    		var t1 = total_r1();
    		var t2 = total_r2();
    		var t3 = total_r3();
    		var t4 = total_r4();
    		
    		var total = (t1+t2+t3+t4);
    		var totalclaim = total.toFixed(2);
    		var total_monthclaim = document.getElementById('total_monthclaim');
    		total_monthclaim.value = totalclaim;
    	}
    	total_all();

What I want is for the

total_all()

to total up all the value from other function and sent it to

<input id="total_monthclaim">