दिए गए विकल्पों में से उस संख्या का चयन करें जो निम्नलिखित श्रृंखला में प्रश्न चिह्न (?) को प्रतिस्थापित कर सकती है: 1, 13, 85, 517, 3109, ?

Seema counted on the fingers of her left hand in the following way: She started by calling the thumb 1, index finger 2, middle finger 3, ring finger 4, and little finger 5. She then reversed direction, calling the ring finger 6, middle finger 7, index finger 8, and thumb 9. Then she reversed direction again, calling the index finger 10, and so on. If she counted up to 1994, on which finger did she end her count?

Which two signs should be interchanged to make the given equation correct? 12 ÷ 3 + 9 × 1 - 6 = 7