Suppose you want to multiply a $5-\text{by}-11$ matrix by a c-by-d matrix.

1. For what value of c will the multiplication be defined?

   Answer (a):

   The multiplication will only be defined if $c = 11$.

2. Given this value of c, what will be the dimensions of the product matrix?

   Answer (b):

   The product matrix will be a $5-\text{by}-d$ matrix.