According to Rankine's fromula, the minimum depth of foundation

• A. <img src="/_files/images/civil-engineering/soil-mechanics-and-foundation-engineering/42-11-177-1.png">
• B. <img src="/_files/images/civil-engineering/soil-mechanics-and-foundation-engineering/42-11-177-2.png">
• C. <img src="/_files/images/civil-engineering/soil-mechanics-and-foundation-engineering/42-11-177-3.png">
• D. <img src="/_files/images/civil-engineering/soil-mechanics-and-foundation-engineering/42-11-177-4.png">