Enbridge Inc ENB.TO and Norway's Yara International ASA YAR.OL said they are planning to invest up to $2.9 billion to build a low-carbon blue ammonia production plant in Texas. March 31 (Reuters) - Futures tracking Canada's main stock index were muted on Friday as investors remained cautious ahead of domestic economic growth data and key U.S. inflation numbers. ET, is expected to reflect a 0.3% rise in January, according to a Reuters poll of economists, compared with a 0.1% fall in the previous month.