Lisa eats pizzas and burritos. Her utility function is

U$($B$,$ Z$)=$ B

$0\mathrm{.}6$Z

$0\mathrm{.}4$

$,$

where Z is the number of pizzas consumed and B is the number of burritos consumed.

The price of burrito is PB and the price of pizza is PZ$.$ Lisa$$s income is W$.$

$($a$)$ If PB $=$ $$4,$ PZ $=$ $$2,$ and W $=100,$ how many pizzas will Lisa buy?

$($b$)$ If the price of a burrito increases to $$10$ while the price of pizzas remains the same,

how many pizzas will Lisa buy?

$($c$)$ What is Lisa$$s demand function for pizza and for burritos? $[$Note: you should get the

functions that depend on PB$,$ PZ and W$.$

$($d$)$ What are the own price elasticities of her demand functions?