Answer:
The slope of the function is ²/₃ and since the second derivative is zero, the concavity doesn't exist.
Explanation:
Given;
x = 6t
y = 4t - 3
point t = 4

The slope of the function is ²/₃
take the second derivative of the function;
the second derivative will be zero since the first derivative is a constant value.

Since the second derivative is zero, the concavity doesn't exist.