Answer:
Rs. 144
Step-by-step explanation:
To what the cost of each pen, divide 90/5
You get 18. So each pen costs 18.
Now multiply 18 by 8 and you would get 144.
So, it would cost Rs. 144

Now, If the exponent was negative like you asked....
Answer:
Some details are missing in the question, here are the details ; A proton initially has v = -6.5i + 17j + 13k and then 8.00s later has v = -2.8i + 17j - 9.3k (in meters per seconds).
a) proton's average acceleration in unit vector notation = 0.46i - 2.78k
b) Magnitude = 2.85m/s2
c) angle between and the positive direction of the x axis = 279.39 degree (counter clockwise)
Step-by-step explanation:
The detailed and step by step explanation is as shown in the attachment