union U1 (int a; float b; ); union U2 (char a; double b; ); struct S union U1 ul; union U2 u2; Si Assume that the machine has 1-byte characters, 4-byte integers, 8-byte floating numbers, and 16-byte double-precision floating numbers. Assume the compiler does not reorder the fields, and it leaves no holes in the memory layout. a) (4pt) How many bytes does s occupy? b) (6pt) If the memory address of s starts from 1000, what are the start addresses of s.ul.b and s.u2.b