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 cost of 5 books and 4 pens (A=36, N=9)

S= A×N

  =36 × 9= 324

Sum of average cost of 7 books and 8 pens (A=48, N=15)

S= A×N

  =48× 15= 720

∴ Total cost of 12 books and 12 pens = 320+720

= 1044

Hence, Option B is correct.