Write a program that calculates a sum. Ask the user to enter a vector and the output will

be the sum of the elements in that vector. Calculate the sum of

$($a$)\left[\begin{array}{cccc}1& 2& 3& 4\end{array}\right]$

$($b$)\left[\begin{array}{ccccccc}-1& 3& -5& 7& -9& 11& -13\end{array}\right]$

$($c$)\left[\begin{array}{ccccccccccccc}81& 65& 61& 78& 94& 80& 65& 76& 77& 95& 82& 49& 75\end{array}\right]$

Solution: $($a$)10($b$)-7($c$)978$

Note: DO NOT use the built$-$in sum function that MATLAB has.