## Differential equations: Newton's Law of Cooling

Need help on this one. DE Newton's Law of Cooling

At 9 A.M., a thermometer reading 70°F is taken outdoors where the temperature is

l 5°F. At 9: 05 A.M., the thermometer reading is 45°F. At 9: 10 A.M., the thermometer is

taken back indoors where the temperature is fixed at 70°F. Find (a) the reading at

9: 20 A.M. and (b) when the reading, to the nearest degree, will show the correct

(70°F) indoor temperature.