Oil prices rose on Monday after a three-day break, adding to gains in recent weeks as optimism holds that a production freeze among major producers may be implemented, but volumes were thin as a number of markets remain on holiday for Easter. U.S. crude’s front-month contract was up 50 cents at $39.96 a barrel at 0622 GMT. Last week, the contract rose 2 cents, finishing up for a sixth straight week. Brent’s front-month climbed 45 cents to $40.89 a barrel. Last week, it fell 76 cents, or nearly 2 percent, its first decline in five weeks.