What is the most important problem shown here?
a. Tyvek should be repaired as necessary and taped to headwall and sidewall flashing.
b. New underlayment should be properly installed. EPDM should be bonded to sheathing and be overlapped by felt underlayment in the course immediately above.
c. Headwall flashing should be raised 1/2-inch to allow shingles to be slipped beneath.
d. Sidewall flashing should not be continuous but should be step-flashing installed as the shingles are installed.