Frustrated with the slow pace of work on the 32-km Charkop-Bandra-Mankhurd metro line, top Reliance Infrastructure officials have written to the chief minister detailing how delays by the Mumbai Metropolitan Region Development Authority (MMRDA) and the Central and Western railway authorities have begun to hurt the project. In their 13-page letter sent about a month ago, the officials have said if delays continue, the project will not be financially viable for the R-Infra-led consortium.