Two cross-roads of width 5 m pass through the middle of a rectangle of dimensions
30 m by 20 m. One of the roads is parallel
to the length and the other is parallel
to the breadth. Determine the cost of
construction of the roads if 1 sq. m costs
Rs 15.

Please help me solve this with steps .​

Scores on a university exam are normally distributed with a mean of 78 and a standard deviation of 8. the professor teaching the class declares that a score of 70 or higher is required for a grade of at least “c.” using the 68-95-99.7 rule, what percentage of students failed to earn a grade of at least “c”?