Problem 44952. Find MPG of Lightest Cars

I do not understand why this code failed assertion test even though it yields the correct answer

function mpg = sort_cars(N)
load cars.mat
sorted = sortrows (cars,4)
n = N
mpg = sorted(1:n,2)
end

The output is expected to be a column vector, whereas your code returns a table.

I tried for the solution nearly 20 ways but didn't work. finally took help from the Matlab community and compleated it