Question 1202122
1,2,3,4,5,4,3,2,1
Since the number of pearlsare small it is easy to sum the cost for the string. 25

There are twosequences

1to 5 increasing by 1

6to 9 decreasing by 1

Sn = n/2 (a+l) ( arithmetic  sequence) Sum of n terms
a=1 l=5 n=5

5/2(1+5) =15

Now the other part


4/2(4+1)= 10

10+15=25