$1.$ Lisa and Jason met with the supervisor of the pizza division of a medium$-$sized Italian food supplier. The supervisor explained the two key costs in his division, as follows. Cost Type Number of Units Total Each pizza $3,450$ $$13,4553,450$ $$4,830$ Although Lisa and Jason used this data to estimate a model for the division's costs, they each came up with a different model, as follows. Lisa's cost model Total pizza division cost $=$ $$3\mathrm{.}90($number of pizzas$)+$ $$4,830$ Jason's cost model Total pizza division cost $=$ $$5\mathrm{.}30($number of pizzas$)$ What understanding did Lisa have about the cost behavior of these costs?