NAIROBI (Reuters) - ARM Cement Ltd, Kenya's second-biggest cement producer, reported a 12 percent increase in full-year pretax profit, helped by a vibrant economy attracting foreign companies to build factories. ARM, which trails Bamburi Cement Ltd in capacity, also took advantage of a boom in construction to house a burgeoning middle class. Last year, pretax profit reached 2 billion shillings ($23.17 million) and earnings per share increased to 2.73 shillings from 2.52 shillings, the company said in a statement. ($1 = 86.3000 Kenyan Shillings)