Hi
Calculator and/0r use of Electronic Worksheets Absolutely necessary
x m (x-µ) (x-µ)^2
86 520.8 -434.80 189051.040
135 520.8 -385.80 148841.640
250 520.8 -270.80 73332.640
357 520.8 -163.80 26830.440
447 520.8 -73.80 5446.440
553 520.8 32.20 1036.840
646 520.8 125.20 15675.040
769 520.8 248.20 61603.240
830 520.8 309.20 95604.640
1135 520.8 614.20 377241.640 Sum
5208 994663.600 sum/9 = V
110518.178 sqrt V
SD 332.443
ME = 1.645*332.4/sqrt(10) = 173
CI: 521-173-ME < u < 521 + 173 (348, 694) not listed; B the closest match