please tell me what im doing wrong, i got 19 days and not 18 days like the answer says in the book

1 ...3.16 The Rover 6 is a new custom-designed sports car. An analysis of the task of building the Rover 6 reveals the following list of relevant activities, their immediate predecessors, and their duration: JOB LETTER DESCRIPTION IMMEDIATE NORMAL PREDECESSOR(S) TIME (DAYS) A Start 0 B Design A 8 C Order special accessories B 0.1 D Build frame B 1 E Build doors B 1 F Attach axles, wheels, D 1 - gas tank G Build body shell B 2 - H B 3 Build transmission and drivetrain 1 Fit doors to body shell GE 1 3 J Build engine B 4 Bench-test engine J 2 L Assemble chassis F, H, K 1 M Road-test chassis L 0.5 N Paint body I 2 O Install wiring N 1 Install interior N 1.5 Q 5 Accept delivery of special accessories ] R Mount body and accessories on chassis M, O, P, Q 1 S Road test car R 0.5 T Attach exterior trim S 1 U Finish T 0 3 1 1 a) Draw a network diagram for the project. b) Mark the critical path and state its length. c) If the Rover 6 had to be completed 2 days earlier, would it help to: i) Buy preassembled transmissions and drivetrains? ii) Install robots to halve engine-building time? iii) Speed delivery of special accessories by 3 days? d) How might resources be borrowed from activities on the non- critical path to speed activities on the critical path? PX 3.16 Project Management Precedences; 1 time estimate Enter the times in the appropriate column(s). Enter the precedences, one per column. (Do use commas). Data Immediate Predecessors (1 per column) Activity Time Pred 1 Pred 2 Pred 3 Pred 4 A 0 8A 0.1|b 1 b 1 b 1 d 2b 3 b 1 g e 4 b D C 1 D 2 E BF 4 G 5 H 6 I 7 J 2L M 1 N 2 10 4 5 R 2 1f h k 0.5L 2 i 1 n. 1.5|n 50 1 m o P a 1.5|r 5 S 7 T 3 U 9 . Results 1 s Ot