So is it less than 13bn?

Tanzania is a bog for KE firms. I don't think many KE firms make an economic profit in TZ.

Definitely more than 13bn. Limestone deposits alone minus the factories is more than 13bn

https://www.bloomberg.com/news/articles/2017-11-10/kenya-s-arm-is-said-to-become-next-target-in-africa-cement-wars

ARM Cement Ltd., the Kenyan building-materials supplier, is the newest takeover target in the battle among the world’s biggest cement makers to expand in Africa, according to people familiar with the matter.

ARM’s owners are exploring a sale, said the people, who asked not to be identified because the talks are private. The Nairobi-based company is currently valued at about $133 million on the Nairobi stock exchange, though the sellers are seeking more than double that amount, the people said. ARM’s two biggest shareholders are CDC Group Plc, a development-finance institution owned by the U.K. government that invested last year, and the founding Paunrana family.

“We are in the process of finding an equity and a strategic buyer to inject equity into the business,” ARM Managing Director Pradeep Paunrana said by phone on Friday. “The process is on and we expect over the next few weeks to complete that process.”