The simple interest on Rs$.10$ for $4$ months at the rate of $3$ paise per rupees per month is

a$)$ Rs$\mathrm{.}1\mathrm{.}20$

b$)$ Rs$\mathrm{.}1\mathrm{.}60$

c$)$ Rs$\mathrm{.}2\mathrm{.}40$

d$)$ Rs$\mathrm{.}3\mathrm{.}60$