Answer
$371.3cm^{-1}$
Work Step by Step
We can calculate the number of lines per centimeter on the grating as follows:
$N=\frac{sin\theta}{m\lambda}$
We plug in the known values to obtain:
$N=\frac{sin(1.250^{\circ})}{(1)(587.5\times 10^{-9}m)}$
$N=3.713\times 10^{-4}m^{-1}$
$N=3.713\times 10^{-4}(\frac{1}{100cm^{-1}})$
$N=371.3cm^{-1}$
