Saudi Basic Industries Corp faces heavy pressure on its profits due to cheap oil but will keep investing globally to boost capacity in key areas, its acting chief executive said on Sunday after the company reported a 39 plunge in first-quarter profit. SABIC , one of the world’s largest petrochemicals groups and Saudi Arabia’s biggest listed firm, said net profit sank to 3.93 billion riyals ($1.05 billion) in the three months to March 31 from 6.44 billion riyals a year earlier. Its sales values were slashed by the plunge of oil prices, which has dragged down petrochemical product prices.