Briаn cоnsumes оnly pizzа аnd sоda. When the price of a soda is $2 and the price of a slice of pizza is $4, Brian maximizes his utility by buying 5 sodas and 10 slices of pizza. If the marginal utility of the 5th soda is 100 units of utility, then the marginal utility of the 10th slice of pizza must be ________ units of utility.