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 . ​

Ariana starts with 100 milligrams of a radioactive substance. the amount of the substance decreases by 20% each week for a number of weeks, w. the expression 100(1−0.2)w finds the amount of radioactive substance remaining after w weeks. which statement about this expression is true? a) it is the difference between the initial amount and the percent decrease. b) it is the difference between the initial amount and the decay factor after w weeks. c) it is the initial amount raised to the decay factor after w weeks. d) it is the product of the initial amount and the decay factor after w weeks.