A solution is to be kept between 40°C and 45°C.

Let temperature in Celsius be C

Let temperature in Fahrenheit be F

According to the question,

Solution should be kept between 40° C and 45°C

⇒ 40 < C < 45

Multiplying each term by 9/5, we get

⇒ 72 < 9/5 C < 81

Adding 32 to each term, we get

⇒ 104 < 9/5 C + 32 < 113

⇒ 104 < F < 113

Hence, the range of temperature in Fahrenheit should be between 104° F and 113° F.