Answer:
The total effect is 35 out of which income effect is 15 and substitution effect is 20. 
Explanation:
Ross has an income of $1440. 
The price of chocolates (Px) is $10 and donuts (Py) is $9. 
The utility function is given as
U = 0.5xy
Before price rise, Budget line: 
1440 = 10x + 9y,
Consumption is optimal when

0.5y / 0.5x= 1.11
y = 1.11x
Substituting in budget line,
1440 = 10x + 9y = 10x + 9(1.11x)
1440 = 10x + 9.99x
19.99x = 1440
x = 72
y = 1.11x = 79.92 = 80
After price rise, 
Py = 16. 
New budget line: 
1440 = 10x + 16y,
Price ratio 

=
= 0.625
And,


y = 0.625x
Substituting in new budget line: 1440 = 10x + 16y
1440 = 10x + 16(0.625)x
1440 = 20x
X = 72
Y = 0.625x = 45
So, total effect (TE) 
= Decrease in consumption of y 
= 80 - 45 
= 35
With previous (x, y) bundle, 
U = 0.5xy 
U = 0.5 x 72 x 80 
U = 2880
Keeping utility level the same & substituting,
y = 0.625x in utility function:
28800 = 0.5xy





x = 96
Now, putting the value of x, 
y = 
y = 
y = 60
Substitution effect (SE) 
= 80 - 60 
= 20
Income effect 
= TE - SE 
= 35 - 20 
= 15