Freight car loadings over an $18-$week period at a busy port are as follows:

$\backslash$table$[[$Week$,$Number,Week,Number,Week,Number$],[1,340,7,405,13,565],[2,345,8,445,14,570],[3,350,9,485,15,620],[4,345,10,480,16,625],[5,350,11,520,17,630],[6,355,12,560,18,635]]$

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a$.$ Determine a linear trend line for expected freight car loadings. $($Round your in to $2$ decimal places.$)$