I would like you to create a spreadsheet that calculates a weighted average forecast, and charts it as an xy plot, where time is on the x axis.

The data is as follows:

Actual observations at times T$1$ through T$5$ are:

Time $12345$

Observations $5781112$

You should compute the weighted average forecast for Times T$1$ through T$6.$ Note: for the forecast for T$1$ you will have no data yet!

The weighting factors are $0\mathrm{.}25,0\mathrm{.}3,$ and $0\mathrm{.}45,0\mathrm{.}25$ applies to the earliest, $0\mathrm{.}3$ to the middle, and $0\mathrm{.}45$ to the latest.

Explain$/$justify how you derived the forecast at T$1$ and T$2.$