Help with elements of costing

Hello

Can anyone help me understand how to work out this question?

Q: identify the types of cost behaviour described in each statement below. Choose from fixed, variable or semi variable.

At 4000 units the cost is £10000 and at 7500 units the cost is £18760

At 2500 units the cost is £20 per unit and at 12500 units the cost is £4 per unit

At 1200 units the cost is £4100 and at 4800 units the cost is £14900



Thanks for your help!