Answer: 42.84 kg
Step-by-step explanation: Lawn is 17 ft x 20 ft.
Its area is S = 17 x 20 = 340 ft²
Each ft² of lawn accumulates 1050 snowflakes/min, 1ft² = 1050 s.f./min.
As 1 hour has 60 min, the lawn accumulates 63000/hour →
1050 x 60 = 63000
1ft² = 63000s.f./hour
This way, 340 ft² of lawn will accumulate 21,420,000 s.f/hour →
340 x 63000 = 21420000
As 1 snowflake has 2mg, 21,420,000 will have 42,840,000 mg.
As 1kg = 1,000,000 mg
42,840,000/1,000,000 = 42.84 kg