(WARNING: When you write out an expression involving a and h, anytime you want to multiply a times h, you need to leave a single space between the two; i. e. "a h" means "a times h". In contrast, if you write "ah" the computer=webassign thinks that you are talking about a new variable called "ah". Alternatively, use the arithmetic buttons in the pop-up box whenever you want to add, subtract, multiply or divide.):