Since they have to share 20% of their profits with the Al Shabaab Islamist rebels, in order to keep their usual revenue stream at these lower partial ransoms they'll need to increase turnover to 156.25% of the original 6 ships per month (that is: lambda = 9.375 ships per month). Assuming they do not cut ransoms further and keep W at 120 day (4 months), how many ships do they need to average in holding (L) to still maintain the same revenues as before the ransom cuts and profit sharing?