Drop rate calculator

   0
   +
   0
   =
   0

Num1:

     <button data-num1="1">1</button>
     <button data-num1="2">2</button>
     <button data-num1="3">3</button>
     <button data-num1="0">0</button>

Num2:

     <button data-num2="1">1</button>
     <button data-num2="2">2</button>
     <button data-num2="3">3</button>
     <button data-num2="0">0</button>

Op:

     <button data-op="+">+</button>
     <button data-op="-">-</button>
     <button data-op="*">*</button>
     <button data-op="/">/</button>

     <button id="calcButton">Calculate</button>