Answer: C. about 0.71 of the field
Step-by-step explanation:
Since, Roni can mow the field in 30 minutes.
Thus, the work done by Roni in one day = 1/30
And, Allie can mow the field in 75 minutes.
Thus, the work done by Allie in one day = 1/75
⇒ The total work done by Roni and Allie in one day when they worked simultaneously,
= 
= 
= 



⇒ Option C is correct.