Given,

Average cost of 5 books and 4 pens = ₹ 36

Average cost of 7 books and 8 pens = ₹ 48

We know the formula,

$\mathrm{Average} \left(\mathrm{A}\right)=\frac{\mathrm{Sum} \mathrm{of} \mathrm{given} \mathrm{values} \left(\mathrm{S}\right)}{\mathrm{Total} \mathrm{number} \mathrm{of} \mathrm{values} \left(\mathrm{N}\right)}$

Sum of average 30 observations s 45 (A=45, N=30)

S= A×N

 S=45× 30= 1350

Sum of 3 new average 42, 44, 48 are added (A=45, N=33, S=1484)

$$\begin{gathered} \mathrm{A}=\frac{\mathrm{S}}{\mathrm{N}}=\frac{1350+42+44+48}{33} \\ =\frac{1484}{33} \end{gathered}$$

= 44.9

Hence, Option E is correct.