First, we calculate the total are:
Area = 15 x 20
Area = 300 sq ft
Snowflakes accumulated per minute = 1150 x 300
Snowflakes per minute = 345,000 snowflakes per minute
Snowflakes per hour = 345,000 x 60
Snowflakes per hour = 20,700,000
Snowflakes per hour = 20.7 x 10⁶
Mass of one snowflake = 2.2 mg
Mass of one snowflake = 2.2 x 10⁻³ g
Mass of one snowflake = 2.2 x 10⁻⁶ kg
Mass of snow = 20.7 x 10⁶ x 2.2 x 10⁻⁶
Mass of snow = 45.54 kg per hour