Passage: It was in the third building phase of the Tejo Power Station's first period that construction on the industrial naves was completed, both on the boiler rooms and machinery room. In 1928, the same year boiler 11 was installed, it was decided to go ahead with the purchase of the final two low pressure boilers, numbers 8 and 10, from the most frequent supplier, Babcock & Wilcox, due to the delays on the installation of the Humboldt boiler. However, their permanent installation was only concluded at the end of 1930.

Question: Which boiler was delayed in installation?
Humboldt