The reverse saturation current of a Si-based p-n junction

The reverse saturation current of a Si-based p-n junction diode increases 32 times due to a rise in ambient temperature. If the original temperature was 40°C, what is the final temperature?

We know that

I'₀ = I₀ 2		T_f – T_i
		2

32I₀ = I₀ 2		T_f – 40
		10

or 32 = 2		T_f – 40
		10

or 2⁵ = 2		T_f – 40
		10

or 5 =	T_f – 40
	10

or T_f = 90°C
Hence alternative (A) is the correct choice.