the sum of the even numbers between 1 and k is 79 * 80, where k is an odd number, then k =  Choose the correct option:
A) 79	B) 80	C) 81	D) 157	E) 159
<gadget id="calculator">79 * 2</gadget>
<output>158</output>

<gadget id="calculator">158 + 1</gadget>
<output>159</output>

<result>E</result>
the sum of the even numbers between 1 and k is 79 * 80, where k is an odd number, then k =
add(multiply(79, const_2), 1)
"the number of terms in this set would be : n = ( k - 1 ) / 2 ( as k is odd ) last term : k - 1 average would be first term + last term / 2 = ( 2 + k - 1 ) / 2 = ( k + 1 ) / 2 also average : sum / number of terms = 79 * 80 / ( ( k - 1 ) / 2 ) = 158 * 80 / ( k - 1 ) ( k + 1 ) / 2 = 158 * 80 / ( k - 1 ) - - > ( k - 1 ) ( k + 1 ) = 158 * 160 - - > k = 159 answer e ."