Find the area of the shaded figure

The other day I had the opportunity to drop by my department head's office. He's a friendly guy and, on the rare opportunities that I have to pay him a visit, we have had enjoyable conversations.

While I was in his office, I asked him, "Sir, what is the secret of your success?"

He said, "Two words."

"And, Sir, what are they?"

"Right decisions."

"But how do you make right decisions?"

"One word," he responded.

"And, Sir, what is that?"

"Experience."

"And how do you get experience?"

"Two words."

"And, Sir what are they?"

"Wrong decisions."