The following information is available for a company:

Year $1$ Year $2$ Year $3$ Year $4$

Sales$/$production $($units$)134,400142,600151,200150,200$

Total costs $()271,000289,144313,180318,900$

Cost inflation index $100107115120$

Required:

$1.$ Determine a linear function for total costs per annum $($at Year $1$ prices$)$ from the above data, using the high$-$low method. $($Do not round variable cost element in the intermediate calculations. Round the first coefficient to $3$ decimal places and the second coefficient the to nearest whole number.$)$