A demand forecast for water heaters for the next few years is needed to help decide whether to add new production capacity. The company's sales history $($in thousands of units$)$ is shown in the table below. Use exponential smoothing with trend adjustment, to forecast demand for period $6.$ The initial forecast for period $1$ was $11$ units; the initial estimate of trend was $0.$ The smoothing constants are $=\mathrm{.}3$ and $=\mathrm{.}3$

Period

Actual

$1$

$12$

$2$

$15$

$3$

$16$

$4$

$16$

$5$

$18$

$6$

$20$