A Methods and Measurements Analyst needs to develop a time standard for a certain task. The task involves use of ruler, square, and portable electric saw to mark and cut the "notch" in a rafter $($a standard carpentry task of home construction$).$ In a preliminary study, he observed one of his workers perform this task five times. The observations were made in an air$-$conditioned, well$-$lighted training facility, at ground level, with all tools and equipment clean and readily available.

Observation:

$1$

$2$

$3$

$4$

$5$

Average time

Normal time

Standard time

Task time $($seconds$)$:

$20$

$74$

$80$

$83$

$76$

X

Y

Z

What is the actual average time X for this task? $($be careful$)$

A$.$

$67$

B$.$

$78$

C$.$

$79$

D$.$

$82$

E$.$

$63$