Write a function that returns the sum of all the elements in a specified column in a matrix using

the following header:

def sumColumn$($m$,$ columnIndex$)$:

Write a main function that prompts the user to enter a $3-$by$-4$ matrix of numbers, calls the above

function, and displays the sum of each column.

Here are sample runs:

Enter a $3-$by$-4$ matrix row $0$: $1\mathrm{.}5234$

Enter a $3-$by$-4$ matrix row $1$: $5\mathrm{.}5678$

Enter a $3-$by$-4$ matrix row $2$: $9\mathrm{.}5131$

Sum of the elements at column $0$ is $16\mathrm{.}5$

Sum of the elements at column $1$ is $9\mathrm{.}0$

Sum of the elements at column $2$ is $13\mathrm{.}0$

Sum of the elements at column $3$ is $13\mathrm{.}0$