Answer:
(a) $\mathrm {R-M + 25}$.
Here $\mathrm{M\le R}$ is the sum total of rotis made.
$\mathrm {S \le M}$ are the total rotis sold.
$\therefore$ The set of possible values: $ {0, 1, 2, \cdots , \mathrm {2R}}$
(b) By preparing $1$ roti and doing nothing else, minimum Rs $=0$.
Maximum rupees $=\mathrm {2P + 1}$
She can make her first roti and then sell for the $2$ Rs.
Total trips she can make to the kitchen $=\mathbf P$ which doubles her money with each trip.