Answer:
option A
Step-by-step explanation:
given,
10% A grades 80% B grades 10% C grades
This year, managers with scores less than 35 received C's and those with scores above 425 received A's.
The mean has to be middle of two corresponding cutoff value
μ = 230
Cutoff Off C grade corresponds with the area of 0.10 is table A.
corresponding z- score according to Table A
Z = -1.28
now, standard deviation
σ = 152.3
Correct answer is option A