Selective anticancer agent that is useful for the treatment of chronic myeloid leukemia

Imatinib is a selective anticancer agent that is useful for the treatment of chronic myeloid leukemia, and methotrexate is a chemotherapeutic agent that is an effective treatment for many types of cancer.

a) Explain how each of these agents is able to affect cancer cells without affecting most normal cells. (5 marks)
b) Explain why imatinib is effective in only a few types of cancer whereas methotrexate is effective against many.
(5 marks)