Double whole note either of two ways: by a hollow oval note head, like a whole note, with one or two vertical lines on either side, as on the left of the image, or as the rectangular shape also found in older notation, shown in the middle of the image (; ). Because it lasts longer than a bar in most modern time signatures in common use, the breve is rarely encountered except in English music, where the half-note is often used as the beat unit . A related symbol is the double whole rest (double rest or breve rest), which usually denotes
Time value of money is to emphasize that "u" is a "parameter" (fixed in any instance—the time when the cash flow will occur), while "t" is a "variable" (time). In other words, future cash flows are exponentially discounted (exp) by the sum (integral, formula_44) of the future discount rates (formula_45 for future, "r"("v") for discount rates), while past cash flows are worth 0 (formula_46), because they have already occurred. Note that the value "at" the moment of a cash flow is not well-defined – there is a discontinuity at that point, and one can use a convention (assume cash flows have already occurred, or