high/low method with changes in the variable cost per unit,for example:2003 output total cost 26 6566 30 6510 33 6800 44 6985 48 7380 50 7310 when output is 80 units or more,another factory unit must be rented and fixed costs therefore increase by 100%. Variable cost per unit is forecast to rise by 10% in 2004. Explain me pls.