I thin the answer is D.DF
The least number of quadratic system can have is Two real solutions or no real solutions.
If you would like to know how many hours did Judd work outside, you can calculate this using the following steps:
40 hours
outside: 7/10 of the hours = 7/10 * 40 hours = 7/10 * 40 = 28 hours
Judd worked 28 hours outside.