A decimal point is a dot or period that is placed after a whole number. Every number has a decimal point. For example, 1.243 has one. Also, 5. has a decimal point. They are just sometimes invisible. When you use a decimal point, it means that the number has a part of something added to it.
The answer could be 70a+21b
Acute usually means below or exactly 90°, so the greatest would be 90
60 minutes. Take how far it is above ground (20 m) and add it to the absolute value of how far it is below ground (340 m) to get 360 meters, which you divide by the rate of descent (6 m/min) to get 60 minutes.
