$.$ Lisa is a purchasing agent for Highland Sales Company $($HSC$).$ Her supervisor, Jack, gives Lisa written authority to buy as many computers and peripheral devices as necessary for HSC$$s operations. The next day Jack calls Lisa and tells her to buy only $50$ notebook computers and nothing else. Lisa shows the written authorization to Easy Computer, Inc. and enters into a contract with Easy to buy $70$ notebook computers and a selection of peripheral devices such as printers scanners and extra storage media. Easy Computer, Inc. ships the order to HSC$.$

A$.$ Is HSC liable to Easy Computer, Inc. under the contract?

B$.$ Is Lisa liable?

C$.$ In each case, If so$,$ why? If not, why?