1ft = 3.048 dm
volume = 12*11*8 ft^3 = 12*11*8*(3.048) dm^3
                                            Â
=29902.6 dm^3
                                            Â
=29902.6 L
density of air = 1.2 g/L
mass of air = density * volume
                      Â
=1.2 * 29902.6
                      Â
= 35883.11 g
for incandescent bulb:
Heat given in 1 hor = P*t
      = 75 W*3600 s
      = 270,000 J
use:
heat = m*C*delta Ti
270000 = 35883.11*1.007*delta Ti
delta Ti = 7.5 oC
for fluorescent bulb:
Heat given in 1 hor = P*t
      = 18 W*3600 s
      = 64800 J
use:
heat = m*C*delta TF
64800 = 35883.11*1.007*delta TF
delta TF= 1.58 oC
Ratio = 7.5/1.58
          =
4.75
Answer:4.75
