The straight line joining the points A(3,-5) and B(6,k) has a gradient of 4.
Gradient is the slope
So the slope of the line joining the points A(3,-5) and B(6,k) is 4
Slope of line joining two points = 
A(3,-5) and B(6,k) are (x1,y1) and (x2,y2)
slope = 
slope = 
We know slope =4

Cross multiply and solve for k
k + 5 = 12
k = 7
The value of k = 7
The range of the given relation is D. R = {-1, 3, 5, 8}.
Step-by-step explanation:
Step 1:
The range of a relation is the second set of values while the domain constitutes the first set of values.
There are 4 given relations with two sets of values so there would be 4 domain values and 4 range values.
Step 2:
The range of (1, -1) = -1,
The range of (2, 3) = 3,
The range of (3, 5) = 5,
The range of (4, 8) = 8.
Combining these values we get the range as {-1, 3, 5, 8} which is option D.
Vertical line has no slope. so only look at the x value. x=-4.
3.72÷1.5=2.48
$2.48 per pound