Answer:
Let the amount of consultant charges be y
and let the hours of work be x.
From the given condition, we have
(4, 400) and (5, 450)
Use Slope intercept form for two points
and

i,e
......[1]
, where m is the slope which is given by:
.
For the given points (4, 400) and (5, 450);
First calculate the slope:
.
Now, put this value of m in equation [1] ;

Use distributive property on RHS ( i.e,
)

Now, add 400 to both sides of an equation:

Simplify:
y = 50x+200.
or
f(x) = 50x+200, where x be the hours of work.
Therefore, the function that represents the amount the consultant charges for h hours of works ;
f(h) = 50h+200