a$-2.$ Forecast the preceding eight years, and determine the forecast errors. $($Negative answers should be indicated by a minus sign. Do not round intermediate calculations and round your final answer to $2$ decimal places.$)$

Year Sales$(000)$ Forecast Error Error$\backslash$Lambda $2$

$137\mathrm{.}30$

$38\mathrm{.}525$

$-1\mathrm{.}225$

$244\mathrm{.}40$

$42\mathrm{.}614$

$1\mathrm{.}786$

$347\mathrm{.}20$

$46\mathrm{.}703$

$0\mathrm{.}497$

$451\mathrm{.}40$

$50\mathrm{.}792$

$0\mathrm{.}608$

$554\mathrm{.}40$

$54\mathrm{.}881$

$-0\mathrm{.}481$

$657\mathrm{.}00$

$58\mathrm{.}97$

$-1\mathrm{.}97$

$761\mathrm{.}40$

$63\mathrm{.}059$

$-1\mathrm{.}659$

$869\mathrm{.}60$

$67\mathrm{.}148$

$-2\mathrm{.}452$