(a) Largest positive value:
This happens when all significant (mantissa) bits are 1, and the exponent bits are all 1.
$=(b)^{p-1} -1\times (b)^{X-q}$
Smallest positive value:
This happens when the LSB of mantissa is 1 and the exponent bits are 0 so that subtracting the bias gives the largest negative value possible for exponent
$=1 \times (b)^{-q}$