Answer and Explanation:
Here, in this particular case it is given that Les had agreed to install a modem and hard disk on Marilee's personal computer in return for the four of her textbooks, but apparently Les only installs the modem and further refuses to install the hard disk unless and until Marliee provides her with two more text books. Therefore in this case, Marliee can further tend to sue Les for the breach of the agreement, since in this case Les already had the duty to install both modem and hard disk.