Answer:
A) 365.28
B) first year: 
25.37593 
and during last year:
 66.49
C) straight line will generate interest evenly throughout the life of the bond:
(1,000 - 365.28) / 15 = 42.32 interest expense per year
Step-by-step explanation:
We solve for the present value of a lump sum as the zero-coupon is a bond with no interest payment only maturity.
Is important to notice the required return is compounding semiannually thus, there are two payment per year and the rate should be halved:
 
 
 
 Maturity $1,000.00 
 time 30.00 (15 years x 2 payment per year)
 rate 0.03500 (7% annual compounding semiannually)
 
 
 
 PV 356.2784 
Now, we calculate the interest expense for the year
356.2784 x (1.035 x 1.035 -1 ) = 25.37593 
For the last year
 
 
 
 Maturity $1,000.00 
 time 2.00
 rate 0.03500
 
 
 
 PV 933.5107 
1000 maturity - 933.51 value one year before = 66.49