Consider the supply chain illustrated$$ below:

Manufacturer

Distributor

Wholesaler

Retailer

The diagram contains $4$ rectangles. From left to right the rectangles are labeled "Manufacturer," "Distributor," "Wholesaler," and "Retailer." There are arrows pointing from left to right between each box as follows: Manufacturer to Distributor, Distributor to Wholesaler, and Wholesaler to Retailer.

Last year the$$ retailer's weekly variance of demand was $220$ units. The variance of orders was $480,600,770,$ and $1,380$units$,$ for the$$ retailer, wholesaler,$$ distributor, and$$ manufacturer, respectively.$($Note that the variance of orders equals the variance of demand for that$$ firm's supplier.$)$ The Bullwhip measure for the retailer is